Communication networks include wired and wireless networks. Example wired networks include the Public Switched Telephone Network (PSTN) and the Ethernet. Example wireless networks include cellular networks as well as unlicensed wireless networks that connect to wired networks. Calls and other communication sessions may be connected across both wired and wireless networks.
Long Term Evolution (LTE) is a wireless communications standard that is promulgated by the 3rd Generation Partnership Project (3GPP) as a major fourth generation (4G) communications standard. Evolved Universal Terrestrial Radio Access Network (E-UTRAN) is the air interface of 3GPP's LTE upgrade path for wireless networks. The E-UTRAN protocol stack has multiple layers including PDCP, Radio Link Control (RLC), Medium Access Control (MAC), and physical layer (PHY). The PDCP layer provides transport for user payload, such as Internet Protocol (IP) packets in the user plane and/or control plane data in the control plane, depending on the radio bearer for which it is carrying data. In operation, the PDCP layer may receive PDU from lower layers. The received PDU is a Service Data Unit (SDU) that can be delivered to upper layers.
Like reference symbols in the various drawings indicate like elements.